New torsional oscillator experiments with plastically deformed helium show that what was thought to be defect-controlled supersolidity at low temperature may in fact be high-temperature softening from nonsuperfluid defect motion in the crystalline structure.

The existence, through statistical fluctuation, of arbitrarily large regions with a certain order in an otherwise disordered system, allow one to set bounds on various important thermodynamic properties.

Experiments indicate that, as in a superfluid, mass can flow through solid helium-4 without viscous resistance. Recent calculations shed light on how this may happen thanks to defects in the crystal lattice.